Actuator load and slew rate limiting via pressure throttling shutoff valve

Abstract

A system includes a control valve with a first control port and a second control port. An actuator of the system includes a piston between an extend chamber and a retract chamber. The system also includes a shutoff valve fluidically connected between the control valve and the actuator. The shutoff valve is passively controlled by a pressure differential between the extend chamber and the retract chamber. If the pressure differential between the extend chamber and the retract chamber exceeds normal operating pressures for the actuator, the shutoff valve closes to stop pressure and flow communication between the control valve and the actuator, thereby pausing the actuator. When the pressure differential between the extend chamber and the retract chamber returns to the normal operating pressures for the actuator, the shutoff valve passively returns to an equilibrium position that allows the actuator to resume operation.

The invention claimed is: 
     
         1 . An actuation system comprising:
 an electrohydraulic servo valve comprising:
 a first control port; and 
 a second control port; 
   a hydraulic actuator comprising:
 an actuator housing; 
 a piston inside the actuator housing; 
 an extend chamber in the actuator housing on a first side of the piston; 
 a retract chamber in the actuator housing on a second side of the piston; and 
 a linkage arm extending from the piston through the actuator housing; 
   a shutoff valve comprising:
 a valve housing extending axially from a first end of the shutoff valve to a second end of the shutoff valve relative to a center axis of the shutoff valve; 
 a first valve seat formed in the valve housing and axially between the first end and the second end of the shutoff valve; 
 a first port extending through the valve housing and axially between the first end of the shutoff valve and the first valve seat, wherein the first port is fluidically connected to the extend chamber of the hydraulic actuator; 
 a second port extending through the valve housing and axially between the first valve seat and the second end of the shutoff valve, wherein the second port is fluidically connected to the first control port; and 
 a third port extending through the valve housing and axially between the second port and the second end of the shutoff valve, wherein the third port is fluidically connected to the second control port or the retract chamber of the hydraulic actuator; 
 a spool inside the valve housing and comprising:
 a land in the valve housing and axially between the first valve seat and the second end of the shutoff valve; and 
 
 a first spring between the spool and the valve housing, wherein the first spring biases the land to an equilibrium position between the second port and the third port. 
   
     
     
         2 . The actuation system of  claim 1 , wherein the shutoff valve further comprises:
 a second valve seat axially between the third port and the second end of the shutoff valve, wherein the third port is fluidically connected to the second control port; and   a fourth port extending through the valve housing and axially between the second valve seat and the second end of the shutoff valve, wherein the fourth port is fluidically connected to the retract chamber of the hydraulic actuator.   
     
     
         3 . The actuation system of  claim 2 , wherein the shutoff valve further comprises:
 a second spring within the valve housing and axially between the spool and the second end of the shutoff valve,   wherein the first spring is within the valve housing and axially between the spool and the first end of the shutoff valve, and   wherein the first spring and the second spring together bias the land to the equilibrium position between the second port and the third port.   
     
     
         4 . The actuation system of  claim 3 , wherein the shutoff valve further comprises:
 a first elastomeric seal on the first valve seat and extending circumferentially about the center axis of the shutoff valve;   a second elastomeric seal on the second valve seat and extending circumferentially about the center axis of the shutoff valve; and   a third elastomeric seal on the land of the spool, wherein the third elastomeric seal extends circumferentially on the land about the center axis and is axially positioned between the second port and the third port.   
     
     
         5 . The actuation system of  claim 4 , wherein the shutoff valve further comprises:
 a first chamber within the valve housing and axially between the first end of the shutoff valve and the land, wherein the first port fluidically connects with the first chamber, and wherein the second port fluidically connects with the first chamber when the land is in the equilibrium position; and   a second chamber within the valve housing and axially between the land and the second end of the shutoff valve, wherein the fourth port fluidically connects with the second chamber, and wherein the third port fluidically connects with the second chamber when the land is in the equilibrium position.   
     
     
         6 . The actuation system of  claim 4 , wherein the spool further comprises:
 a shaft extending axially between the first end and the second end of the shutoff valve, and wherein the land is connected to the shaft;   a second land connected to the shaft and forming a first end of the spool, wherein the second land is axially between the first end of the shutoff valve and the first valve seat;   a third land connected to the shaft and forming a second end of the spool, wherein the third land is axially between the second valve seat and the second end of the shutoff valve;   a first window within the valve housing and axially between the second land and the land, wherein the first port fluidically connects with the first window when the land is in the equilibrium position, and wherein the second port fluidically connects with the first window; and   a second window within the valve housing and axially between the land and the third land, wherein the third port fluidically connects with the second window, and wherein the fourth port fluidically connects with the second window when the land is in the equilibrium position.   
     
     
         7 . The actuation system of  claim 6 , wherein the shutoff valve further comprises:
 a first spring chamber within the valve housing and axially between the first end of the shutoff valve and the second land; and   a second spring chamber within the valve housing and axially between the third land and the second end of the valve housing,   wherein the first spring is in the first spring chamber and the second spring is within the second spring chamber.   
     
     
         8 . The actuation system of  claim 7 , wherein the shutoff valve further comprises:
 a first pressure port extending through the valve housing to fluidically connect with the first spring chamber, and wherein the first pressure port is fluidically connected to the first port; and   a second pressure port extending through the valve housing to fluidically connect with the second spring chamber, and wherein the second pressure port is fluidically connected to the fourth port.   
     
     
         9 . The actuation system of  claim 7 , wherein the shutoff valve further comprises:
 a first pressure port extending through the valve housing to fluidically connect with the first spring chamber, and wherein the first pressure port is fluidically connected to the second port; and   a second pressure port extending through the valve housing to fluidically connect with the second spring chamber, and wherein the second pressure port is fluidically connected to the third port.   
     
     
         10 . The actuation system of  claim 1 , further comprising:
 a second shutoff valve comprising:
 a second valve housing extending axially from a first end of the second shutoff valve to a second end of the second shutoff valve relative to a center axis of the second shutoff valve; 
 a second valve seat formed in the second valve housing and axially between the first end and the second end of the second shutoff valve; 
 a fourth port extending through the second valve housing and axially between the first end of the second shutoff valve and the second valve seat, wherein the fourth port is fluidically connected to the first control port or to the extend chamber of the hydraulic actuator; 
 a fifth port extending through the second valve housing and axially between the fourth port and the second valve seat, wherein the fifth port is fluidically connected to the second control port; and 
 a sixth port extending through the second valve housing and axially between the second valve seat and the second end of the second shutoff valve, wherein the sixth port is fluidically connected to the retract chamber of the hydraulic actuator; 
 a second spool inside the second valve housing and comprising:
 a second land in the second valve housing and axially between the first end of the second shutoff valve and the second valve seat; and 
 
 a second spring between the second spool and the second valve housing, wherein the second spring biases the second land to a second equilibrium position between the fourth port and the fifth port. 
   
     
     
         11 . A shutoff valve comprising:
 a valve housing extending axially from a first end of the shutoff valve to a second end of the shutoff valve relative to a center axis of the shutoff valve;   a first valve seat formed in the valve housing and axially between the first end and the second end of the shutoff valve;   a first port extending through the valve housing and axially between the first end of the shutoff valve and the first valve seat;   a second port extending through the valve housing and axially between the first valve seat and the second end of the shutoff valve; and   a third port extending through the valve housing and axially between the second port and the second end of the shutoff valve;   a spool inside the valve housing and comprising:
 a land in the valve housing and axially between the first valve seat and the second end of the shutoff valve; and 
   a first spring between the spool and the valve housing, wherein the first spring biases the land to an equilibrium position between the second port and the third port.   
     
     
         12 . The actuation system of  claim 11 , wherein the shutoff valve further comprises:
 a second valve seat axially between the third port and the second end of the shutoff valve; and   a fourth port extending through the valve housing and axially between the second valve seat and the second end of the shutoff valve.   
     
     
         13 . The shutoff valve of  claim 12 , wherein the shutoff valve further comprises:
 a second spring within the valve housing and axially between the spool and the second end of the shutoff valve,   wherein the first spring is within the valve housing and axially between the spool and the first end of the shutoff valve, and   wherein the first spring and the second spring together bias the land to the equilibrium position between the second port and the third port.   
     
     
         14 . The shutoff valve of  claim 13 , wherein the shutoff valve further comprises:
 a first elastomeric seal on the first valve seat and extending circumferentially about the center axis of the shutoff valve;   a second elastomeric seal on the second valve seat and extending circumferentially about the center axis of the shutoff valve; and   a third elastomeric seal on the land of the spool, wherein the third elastomeric seal extends circumferentially on the land about the center axis and is axially positioned between the second port and the third port.   
     
     
         15 . The shutoff valve of  claim 14 , wherein the shutoff valve further comprises:
 a first chamber within the valve housing and axially between the first end of the shutoff valve and the land, wherein the first port fluidically connects with the first chamber, and wherein the second port fluidically connects with the first chamber when the land is in the equilibrium position; and   a second chamber within the valve housing and axially between the land and the second end of the shutoff valve, wherein the fourth port fluidically connects with the second chamber, and wherein the third port fluidically connects with the second chamber when the land is in the equilibrium position.   
     
     
         16 . The shutoff valve of  claim 14 , wherein the spool further comprises:
 a shaft extending axially between the first end and the second end of the shutoff valve, and wherein the land is connected to the shaft;   a second land connected to the shaft and forming a first end of the spool, wherein the second land is axially between the first end of the shutoff valve and the first valve seat;   a third land connected to the shaft and forming a second end of the spool, wherein the third land is axially between the second valve seat and the second end of the shutoff valve;   a first window within the valve housing and axially between the second land and the land, wherein the first port fluidically connects with the first window when the land is in the equilibrium position, and wherein the second port fluidically connects with the first window; and   a second window within the valve housing and axially between the land and the third land, wherein the third port fluidically connects with the second window, and wherein the fourth port fluidically connects with the second window when the land is in the equilibrium position.   
     
     
         17 . The shutoff valve of  claim 16 , wherein the shutoff valve further comprises:
 a first spring chamber within the valve housing and axially between the first end of the shutoff valve and the second land; and   a second spring chamber within the valve housing and axially between the third land and the second end of the valve housing,   wherein the first spring is in the first spring chamber and the second spring is within the second spring chamber.   
     
     
         18 . The shutoff valve of  claim 17 , wherein the shutoff valve further comprises:
 a first pressure port extending through the valve housing to fluidically connect with the first spring chamber, and wherein the first pressure port is fluidically connected to the first port; and   a second pressure port extending through the valve housing to fluidically connect with the second spring chamber, and wherein the second pressure port is fluidically connected to the fourth port.   
     
     
         19 . The shutoff valve of  claim 17 , wherein the shutoff valve further comprises:
 a first pressure port extending through the valve housing to fluidically connect with the first spring chamber, and wherein the first pressure port is fluidically connected to the second port; and   a second pressure port extending through the valve housing to fluidically connect with the second spring chamber, and wherein the second pressure port is fluidically connected to the third port.   
     
     
         20 . An actuation system comprising:
 an electrohydraulic servo valve comprising:
 a first control port; and 
 a second control port; 
   a hydraulic actuator comprising:
 an actuator housing; 
 a piston inside the actuator housing; 
 an extend chamber in the actuator housing on a first side of the piston; 
 a retract chamber in the actuator housing on a second side of the piston; and 
 a linkage arm extending from the piston through the actuator housing; 
   a shutoff valve fluidically connecting the first control port to the extend chamber and/or fluidically connecting the second control port to the retract chamber, wherein the shutoff valve comprises:
 a valve housing; 
 a spool in the valve housing; 
 at least one spring, wherein the at least one spring biases the spool to an equilibrium position that permits fluid and pressure transfer between the electrohydraulic servo valve and the hydraulic actuator; and 
 a valve seat that contacts the spool to close fluid and pressure transfer between the electrohydraulic servo valve and the hydraulic actuator when the spool moves out of the equilibrium position.